I think I have the answers to my questions:
1. Unlikely to buy such a guitar ready made off-the-shelf
2. Thanks to this little quote from the Custom Orders page of the site, just about any kit will do:
Body routing: any configuration of pickups (single coil/humbucker/mini-humbucker/P90/JB, PB or bass humbucker), plus the controls and the control cavity routing to your preference. You can even order a blank body, with no routing except for the neck pocket.
This one definitely wouldn't make it past the Minister of Finance any time soon, so I'm in no rush to move on it. All the same, it can be an exciting process to start designing it in my head.
Here's what I'm thinking:
Bridge humbucker, P90 middle, single coil in the neck.
Separate volume and tone knob for each. Push/pull knob on bridge volume for coil tap purposes. 5 way selector switch. Massive control cavity required!!!
Kit:
I've always had my eye on the PBG-2. They're not available right now, but neither are my funds. All in good time.
Pick ups:
Looks like I'll be giving Toneriders a good go
TONERIDER TRH1B-GD ROCKSONG BRIDGE- GOLD (HUMBUCKER)
TONERIDER R90B REBEL 90 BRIDGE – GOLD
TONERIDER TRT2N-GD HOT CLASSICS NECK PICKUP
...and of course I'll need gold hardware to go with those
I've no idea what I'm going to do for a finish, but I'm willing to bet it'll be a lot of fun to play.